Has the concept of making use of solar power on commercial airliners come up as a way to reduce the amount of fuel consumption and power the likes of AC generators, IFE etc? During the current tough times, would this not be of use to the airlines who are bleeding like never before? Most aircraft fly above the clouds, so getting powered up should not be an issue...

Nice thought but many flights go for 12 hours or more in darkness, like those between LAX-SYD at certain times of the year and especially the very long 'polar' routes.

In your part of the world the height of the sun above the horizon is comparatively shallow even in mid summer, and the energy is attenuated because it passes through the air at a more oblique angle especially in the long mid summer 'white' nights.

I have actually wondered that before. Now as Antares has pointed out, it really couldn't be relied on for every flight. I was thinking that, depending on if there is a cost benefit and weight benefit, maybe it was something that supplemented the generators, in the air or on the ground.

Another issue that comes to mind is, how many solar panels would be needed to be a benefit and where would they go?

In the end, it would just be interesting to know if anyone with power at either A or B have had it considered at all. It might even be something that is better answered by the Tech/Ops people.

That would not help the airlines at all. That would only hurt them. The costs that would be required to develop such a surface would be way too much for one airline to front. The surfaces would be EXTREMELY sensitive. The a/c would probably only allowed to run certain routes. My parents looked at putting solar panels into the roof of our house. The cost was said to make itself up in 5-10 years. There would be just far too much involved in such an idea. A/c are run hard and serviced only when they need to be. The less they have to be fixed/touched the more $$ the airline can make by running that a/c in their system.

I have to second Matt. The initial cost, added weight, and extra maintenance costs would far outweigh any fuel savings due to the decreased electrical demands on the generators. It wouldn't be feasible with current solar technology to provide all of the electrical power for an airliner. Even if the entire structure were covered with solar panels, their combined output would only be a fraction of that of one generator. Even if future panels approached 100% efficiency they still couldn't provide enough power. Nice idea but not practical.

What about using solar power on the ground instead of APU's? Just place the panelsd on the roof of the terminal. Im not sure where I read it, probably in Flying, but there was an article about solar powered runway and taxiway lights. If any one has that article let me know.

This goes along with something I've been wondering for a long time. What research is being done on aircraft to eliminate the need to oil-based fuels. I'm not sure hydrogen fuel cells would work, as it would require the combustion of hydrogen gas, a very dangerous and nearly uncontrolable reaction. All new engine technology, such as scramjets, still use oil-based fuels. The same with composites...99% of all plastics and polymers are made from oil. Jet engines and turbines require a combustion reaction to heat air, so what, other than oil, can be used that is cheap and available in huge quantities?

My thinking is that it doesnt reduce the efficiency of the jet engine by much if an electrical power generation unit is attached to it (Not literally attached of course, but some of the mechanical energy from the jet is transferred to electrical generator). Mechanical energy that is used for production of electricity needed to power an aircraft is indeed a lot, but is negligent in comparison with amount of mechanical energy produced by a jet engine. I mean two engines that produce enough force to propel a 100ton piece of equipment through the air says its a lot of mechanical power in my book. Solar power can possibly replace APU, but, would YOU BE WILLING to risk having a solar panel instead of gas powered APU.

I just want to mention, that I have never in my life designed an aircraft, or any of its components, and dont know if i am right or wrong. this is just my opinion which is based on some real life designs that i saw.

Quoting Concentriq (Reply 7):Solar power can possibly replace APU, but, would YOU BE WILLING to risk having a solar panel instead of gas powered APU.

Solar power cannot replace an APU, period. Many people are enamored of solar power, but don't comprehend how little power their really is. Suppose you took an aircraft the size of a 777, and covered it's entire planform area with solar cells. And then, since this is a pipe dream, let's pretend that we have 100% efficiency, or in other words, the cells convert 100% of the sunlight that hits them, into usable energy on board the aircraft.

If you are in a temperate latitude, you won't be able to generate but a couple hundred kilowatts. Now, that might be enough to power the airplane until you need to start the engines, but then we wake up from said pipe dream and realize that solar cells are only about 10% efficient. Then we throw in latitude effects, cloud cover, aircraft orientation (hey, building cast shadows), and of course, that pesky night time when no sunlight falls upon half the earth's surface at all -- and we realize it's pointless.

Ah, but I must scurry now! My flight from CLE to ATL has been delayed 4.5 hours, and we have to board NOW!

Not to mention the weight of the conversion equipment to turn solar energy into a reliable source. 14V isn't just generated by the sun without going through conditioning, and the weight of such rectifying equipment onboard would almost certainly outweigh the gain.

Quoting FriendlySkies (Reply 6):What research is being done on aircraft to eliminate the need to oil-based fuels.

Quoting FriendlySkies (Reply 6):Jet engines and turbines require a combustion reaction to heat air, so what, other than oil, can be used that is cheap and available in huge quantities?

Embraer has an Ethanol (alcohool) powered crop duster. Not a jet, but definately one of the only renewable resources powered aircraft out there... probably the only one in actual real world use (although I believe just a few have actually entered service right now). Check out http://www.embraer.com and make a search on their news archive, there was something on just a couple of weeks ago. It's actually "NEIVA," and embraer subsidiary who builds the aircraft.

It's good for farmers because they can save big time on Jet fuel. I believe the savings would be about one third here in Brazil.... but don't quote me on that.

Despite the hype, solar power is very inefficient. About 14% right now when pointed at direct sunlight. No matter what, it always needs a backup and/or storage system. Heavy, heavy batteries and/or generator. The electronics to convert the power weigh relatively little.
Windpower on the other hand..be interesting to see if a wind generator would pay for itself after loss of aircraft efficiency.

Thanks for the great responses... I guess even if the producers and customers wanted to explore it, the fact that it cannot be used in all or most situations is an issue...

How about making use of a fan-like device (dunno what it's called, but that windmill thingy that pops out when fuel runs out to generate power) to generate power? I guess it could cause some sort of drag etc...

The reason solar power has never caught on is that it is a real pain in the arse. You need huge arrays of solar panels to get any useful amount of energy from the sun.

The Citicorp Tower in New York City was built with a slanted roof with the intention of covering it with solar panels which would power the building. After the builders broke ground, however, it was realized that the engineer in charge of the solar power aspect had forgotten to carry a zero in his calculations, and the roof would have had to have been exponentially larger in order to catch enough sunlight to power the building. So we have a beautiful, unique building, but it is powered by old fashioned power plants.

Quoting Mham001 (Reply 11):Windpower on the other hand..be interesting to see if a wind generator would pay for itself after loss of aircraft efficiency.

Your curiosity may be satisfied directly and forthwith: it would be a total disaster. I presume you are talking about using some free airstream energy to power on-board systems during flight, because there is clearly never enough wind on the ground to be useful.

The conversion efficiency of such a device would be only a few percent, such efficiency being defined by the energy recovered by the turbine over the increased energy required to propel the airplane with the device deployed. And there are other screwball effects, too. How do you build a device that can provide good power support at low airspeesd as well as very high Mach numbers? It would be abysmal.

But this doesn't paint the whole picture. The real question is, "Would this be more efficient than the present methods for non-propulsion power generation on board an aircraft?" The present methods are electrical generation and bleed air. Bleed air is a disaster from an efficiency standpoint. Huge amounts of losses are incurred during compression, more during bleeding, and even more during usage. The great irony of bleed air is that it's too hot to be used for HVAC, and must be cooled back down again.

This is why Boeing is so gung-ho about an all-electric 787. Bleed air is a serious pig. An all-electric aircraft will probably be more efficient in all points of the power cycle: generation, transmission, conditioning, and consumption. It is probably also easier to manufacture in the long term, and certainly much easier to design open interfaces.

If it were more efficient to have an APU dedicated to nothing but electrical power, they'd probably do it, except that you'd need two of them to guarantee redundancy.

Quoting GothamSpotter (Reply 14):The Citicorp Tower in New York City was built with a slanted roof with the intention of covering it with solar panels which would power the building. After the builders broke ground, however, it was realized that the engineer in charge of the solar power aspect had forgotten to carry a zero in his calculations, and the roof would have had to have been exponentially larger in order to catch enough sunlight to power the building.

*IF* this story is true, that is one seriously stupid engineer. You have to be a real knucklehead to make this mistake AND have it go undetected all the way through architecture and design certification.

Some simple observations would prevent this in any mildly thoughtful engineer. Suppose the building's total electrical load is just 1 MW. How does this compare to other energy sources you see around you? A typical electric space heater is 1.5 kW. A typical four burner electric stove and oven are 12 kW if they are on full blast. A powerful car engine might be 300 kW at peak power.

Any dingaling should be able to look at a few hundred square meters of surface area and say to themselves, "Self, even in direct sunlight, the surface temperature of this area is at best 150 F. Obviously, there isn't nearly enough power here."

I can forgive somebody with a degree in journalism for making this mistake; they do it all the time. Read nearly any aviation article in the mainstream press.

Just this morning, MSNBC.com was reporting that the quake in Indonesia was 8.2, "almost as powerful as the 9.0 that created the tsunami." Huh? Are you kidding? 8.2 isn't even close to a 9.0! It's several times less potent in amplitude, and 10'x of times less potent in terms of energy released!

Another hilarious example: In the Reagan years, the Pentagon was giving a press briefing on ground-based lasers for use as missile defense in SDI. As the story goes, told by one of the engineers giving the briefing, they were talking about the laser's throughput. They said they need 10 to the sixth Joules to be effective, but were getting only 10 to the third. One journalist in the front row was heard to audibly gasp, "My God! We're halfway there!" He had to be corrected and told that 10^3 is not one half of 10^6; it's 1/1000.

In fact, the more I think about it, the more I doubt the story about this building. It's just so... obvious. Not to mention it's not at a latitude that makes it useful. Definitely a sackable offense, if true.

Quoting ContnlEliteCMH (Reply 15):
If it were more efficient to have an APU dedicated to nothing but electrical power, they'd probably do it, except that you'd need two of them to guarantee redundancy.

This is exactly what the 787 will have, the APU will generate electricity only. And what's even cooler, Boeing is building-in a provision that will allow a fuel cell system to replace the turbine APU if/when fuel cells reach the power density required of the function.

Quoting ContnlEliteCMH (Reply 16):Another hilarious example: In the Reagan years, the Pentagon was giving a press briefing on ground-based lasers for use as missile defense in SDI. As the story goes, told by one of the engineers giving the briefing, they were talking about the laser's throughput. They said they need 10 to the sixth Joules to be effective, but were getting only 10 to the third. One journalist in the front row was heard to audibly gasp, "My God! We're halfway there!" He had to be corrected and told that 10^3 is not one half of 10^6; it's 1/1000.

Actual testing during the Carter administration showed that 10^3 Joules/cm2 could shoot down real missiles during boost. The Reagan administration's 10^6 standard was intended to turn the Carter administration's program for building real, imperfect weapons into a welfare program for well-connected scientists that would never be able to meet the standard. The really hilarious part: 7x10^3 Joules/cm2 is the total energy flux on the surface of the sun.

I always find it funny that Fuel Cell technology has not really advanced too far. The technology was invented in the 1950s for use in the Gemini and Apollo programs. The Fuel cells in the Gemini craft were the size of beach balls and could produce up to 14 days of water and electricity. The ones in the Apollo SM were almost the same as Gemini's but more efficient and could serve 3 men for 14 days traveling more than 500,000 miles (Round trip to the moon plus 3 days in lunar orbit). Now think about this...300 people on a plane traveling 8000nm for 12 hours in 2005.

Thirty plus years later and we have not gone too much further. Hmmm I guess we just don't want to challenge ourselves to advance technology.
If NASA could do it in 1964 (First flight with fuel cells) why can't we do it in 2005?

This week the World EXPO started in Aichi, Japan. Toyota introduced buses that runs on fuelcells. The hydrogen comes from garbage produced at the EXPO site. The garbage also produces electricity for the park. Supplemental electricity comes from windmills on the coast.

Think of the possibilities. Airports take garbage produced by travelers and on airplanes and use it to make their own electicity which cuts costs. They use solar cells on the roofs to supplement energy. They can produce hydrogen for Fuel Cells used in Airplanes and the buses running around the airport. The Airplanes use the fuel cells to produce water, electricity and fresh oxygen.

Of course the technology is still weak. But we must find ways to reduce use of petroleum in aircraft. We can make them efficient and that is good but eventually we need something new. If you have any ideas...patent them and wait to make your millions.

Thanks for the heads up on Aichi. Perhaps the environmental crisis will at last put reliable mass produced fuel cell powered cars into use, and as you indicate, not a moment too soon.

However the huge issue for aircraft remains that they cannot be allowed to burn hydrogen at high levels without even more adversely affecting the environment than we do with kerosene. That is because a massive increase in water vapour in the upper atmosphere would multiply the existing green house gas effect, a consequence to be avoided at all costs.

We sure need something totally new to power our jets in the not too distant future.

Quoting UA777222 (Reply 3):Great idea just not fit for the aviation industry.

Yet...I'm thinking 100 years the way people are now. If we were serious and started now, I'm thinking 20 years for an RJ equivalent electric airliner, it would appear turboprop on the outside.

If no one believes it will work they are not going to invest in it, hence we go in circles: If no one invests in it, it causes more and more people to believe it probably will not work, why risk spending money in the first place?!

It is that simple, really. Belief runs a market, nothing else, money is a medium or a reason.

I think rather we run solar-celled planes at certain peak daytime routes and have fuel burners at night and non-peak flights, would that not be a fuel savings to consider? Again, this may be 20-100 years down the line, it depends highly on people to have enough belief in a technology or enough faith in it's evolution, so to speak.

Money is never an object, if you believe you need or want to take a flight somewhere, you will purchase the tickets. Why do you think so many people are in debt to their eyebrows, they do not think about the money as much as their belief that they need/want things.

Once a group of people figures this out, they take control of their perspective industries rather quickly for a period of time.

The meaning of life is curiosity; we were put on this planet to explore opportunities.

Quoting DfwRevolution (Reply 17):This is exactly what the 787 will have, the APU will generate electricity only. And what's even cooler, Boeing is building-in a provision that will allow a fuel cell system to replace the turbine APU if/when fuel cells reach the power density required of the function.

Actually, I was suggesting that if the APU could provide all the power during flight, they wouldn't put generators on the engines. I suspect that redundancy is a big problem, however.

Quoting Lehpron (Reply 21):It is that simple, really. Belief runs a market, nothing else, money is a medium or a reason.

I think rather we run solar-celled planes at certain peak daytime routes and have fuel burners at night and non-peak flights, would that not be a fuel savings to consider?

Belief (of which I have an abundance) is always tempered by fact. It was believed that the sun orbited the earth; of course, the opposite is true.

If you are suggesting solar power as a means of *propulsion*, then I submit that your imagination has gotten the better of your reason. Again, belief is tempered by fact and the facts on solar power are clear: there isn't even remotely enough of it hitting an airframe, at any point in time, at any latitude, to generate enough power for propulsion. Do the math, and you must arrive at the same conclusion. No amount of belief will change this.

I personally like the idea a lot, but you have some obvious drawbacks.

You need to open up the fuselage to install the solar cells underneath and cover it up by some sort of stable plastics.

After you have found out how you do it, you look for a place where to install them.

One picks the wings: The only area where it would be possible is already marked on the wing with a black line including the words (e.g.) "walk inside". After having built-in the solar arrays, these areas are not going to be stepped on again. And... how about the flexibility of solar arrays? Wings need to flexible in turbulence areas. AFAIK, solar array crystal structures are brittle, they break apart easily. And would you like to have spark producing inoperative solar panels above some tens of tons of kerosene?

So another one picks the fuselage top: Now a question to our aircraft builders to correct me if I am wrong. If you open up a fuselage on top and close it again, but with a different material or bend structure as case to hold something, your final stability is lower than before.

The bottom line is:
Kerosene needs to become much more scarce to let this technology become a success in airliners.

25 DfwRevolution
: The electric demands of the Apollo spacecraft were extremly low by today's standards. The output of the Service Module fuel cell stack was roughly 67

26 AmericanPilot
: Aircraft only use about 4% of all fuel refined on the planet. That includes General aviation and airliners. Fly safe and have fun! -Chris

27 MD11Engineer
: In most northern hemisphere industrialised countries, the biggest amount of energy is used for heating the houses in winter (in some countries a very